1. Field of the Invention
The present invention relates to a high-frequency module in which a high-frequency device-mounting package mounting a high-frequency device operating on high-frequency signals of from a microwave band to a millimeter-wave band, is mounted on an external circuit board. More particularly, the invention relates to a high-frequency module in which a high-frequency device-mounting package (hereinafter often referred to simply as high-frequency package) is connected to an external circuit board without deteriorating characteristics of the high-frequency signals.
2. Description of the Prior Art
Conventional representative high-frequency modules equipped with a high-frequency package mounting a high-frequency device that operates on high-frequency signals of microwaves and millimeter waves, have structures as shown in FIGS. 11a and 11b. 
Referring, for example, to FIG. 11a, a high-frequency package 80 comprises a dielectric substrate 82 mounting a high-frequency device 81 which is air-tightly sealed in a cavity 85 formed by a frame 83 and a closure 84. On the surface of the dielectric substrate 82 are formed high-frequency signal transmission lines (hereinafter often referred to simply as high-frequency lines) 86 such as microstrip lines connected to the high-frequency device 81. The high-frequency lines 86 are drawn out of the cavity 85 through the frame 83 and extend to the back surface of the dielectric substrate 82 passing over the side surfaces of the dielectric substrate 82. That is, the high-frequency lines 86 on the back surface of the dielectric substrate 82 are connected to high-frequency lines 88 formed on an external circuit board 87 such as mother board through an electrically conducting material 89 such as solder. High-frequency signals are input to the high-frequency device 81 through the high-frequency lines 86, or high-frequency signals are output to the high-frequency lines 86 from the high-frequency device 81. In the high-frequency module equipped with a plurality of high-frequency packages 80 as shown in FIG. 11a, furthermore, the high-frequency lines 86 on the back surface of the dielectric substrate 82 of each package 80 are connected to the high-frequency lines 88 of the external circuit board 87, so that the high-frequency packages 80 are electrically connected to each other.
A high-frequency module shown in FIG. 11b has the same structure as the high-frequency module of FIG. 11a except that the high-frequency lines 86 formed on the front and back surfaces of the dielectric substrate 82. of the high-frequency package 80 are connected together using the through-hole conductors 90 penetrating through the dielectric substrate 82. In the high-frequency module of FIG. 11a, the high-frequency lines 86 are drawn to the external side through the frame 83, involving such defects that the high-frequency signals produce reflection loss and radiation loss at portions where the high-frequency lines 86 pass through the frame 83 and that characteristics of the high-frequency signals are deteriorated. Besides, since the high-frequency lines 86 are folded, high-frequency signals of the millimeter band produce a large reflection loss at the folded portions of the high-frequency lines 86, making it difficult to transmit or receive signals. In the high-frequency module of FIG. 11b, on the other hand, the high-frequency lines 86 formed on the front and back surfaces of the dielectric substrate 82 are connected together using the through-hole conductors 90, offering an advantage in that the above-mentioned reflection loss and radiation loss are decreased.
In the above-mentioned high-frequency modules of FIGS. 11a and 11b, however, the high-frequency lines 86 of the high-frequency package are connected to the high-frequency lines 88 of the external circuit board through the electrically conducting adhesive material 89 such as solder, making it very difficult to accomplish the alignment of the patterns of the high-frequency lines 86 and the patterns of the high-frequency lines 88. Depending on the frequency of signals, therefore, there occurs reflection loss due to mismatching of the impedance at the connection portions using the electrically conducting adhesive material 89, whereby the transmission loss so increases that it often becomes difficult to transmit signals of high frequencies.
The object of the present invention, therefore, is to provide a high-frequency module which enables the patterns of high-frequency lines of a high-frequency package to be easily aligned with the patterns of high-frequency lines of an external circuit board, enabling the transmission loss of high-frequency signals to be effectively decreased at the junction portions of these lines.
According to the present invention, there is provided a high-frequency module comprising a high-frequency device-mounting package and an external circuit board; wherein
the high-frequency device-mounting package includes a dielectric substrate having a first grounding layer contained therein, the dielectric substrate mounting a high-frequency device on one surface thereof and having, formed on one surface thereof, first high-frequency signal transmission lines connected to the high-frequency device, and having, formed on the other surface thereof, second high-frequency signal transmission lines coupled to the first high-frequency signal transmission lines;
the external circuit board is constituted by a dielectric board having third high-frequency signal transmission lines and a second grounding layer, the third high-frequency signal transmission lines being formed on one surface of the dielectric board, and the second grounding layer being formed on the other surface of the dielectric board or inside thereof; and
the high-frequency device-mounting package and the external circuit board are arranged side by side, and the second high-frequency signal transmission lines of the high-frequency device-mounting package are electrically connected to the third high-frequency signal transmission
lines of the external circuit board through linear electrically conducting members.
The invention further provides a high-frequency device-mounting package equipped with a dielectric substrate having a grounding layer contained therein; wherein
the dielectric substrate mounts a high-frequency device on one surface thereof and has, formed on one surface thereof, first high-frequency signal transmission lines connected to the high-frequency device, and has, formed on the other surface thereof, second high-frequency signal transmission lines coupled to the first high-frequency signal transmission lines; and
a connection portion is formed at the ends of the second high-frequency signal transmission lines for connecting linear electrically conducting members connected to an external circuit board.
In the high-frequency module of the present invention if briefly described, the high-frequency device-mounting package (high-frequency package) and the external circuit board are arranged side by side, and the second high-frequency signal transmission lines on the package and the third high-frequency signal transmission lines of the external circuit board are connected together through linear electrically conducting members such as wires, ribbons or electrically conducting tapes, making very important features. The module of the present invention having the above-mentioned structure offers an advantage in that when the high-frequency package is mounted on the external circuit board, the patterns of the second high-frequency signal transmission lines of the package can be (easily aligned with the patterns of the third high-frequency signal transmission lines of the external circuit board, producing a small high-frequency signal transmission loss between the lines.
In the present invention, the first high-frequency signal transmission lines formed on one surface of the dielectric substrate in the high-frequency package and connected to the high-frequency device, can be directly connected to the second high-frequency signal transmission lines formed on the other surface of the dielectric substrate by using, for example, through-hole conductors. Desirably, however, they should be electromagnetically coupled together. When they are connected together by using through-hole conductors, the high-frequency signal transmission characteristics may often be deteriorated in the connected portions due to signal transmission loss. When they are electromagnetically coupled together, however, no such loss takes place. These lines can be easily electromagnetically coupled together by forming slots in the grounding layer in the dielectric substrate.
According to the present invention, furthermore, the grounding layer formed in the dielectric substrate in the high-frequency package is partly exposed. By utilizing the exposed surface of the grounding layer, the grounding layer of the package is connected to the grounding layer formed on the external circuit board or to the grounding layer of other package, in order to easily maintain constant at all times the gap between the grounding layer and the high-frequency signal transmission lines formed on the package or on the external circuit board thereby to decrease the transmission loss of high-frequency signals.